1. Field of the Invention
The present invention relates to marine vehicles, and more particularly, to jet pump driven watercraft propulsion systems.
2. Description of the Related Art
Several designs for marine craft jet propulsion adjustable venturi systems have been designed in the past. None of them, however, includes a low cost and robust system with minimal moving parts in critical areas resulting in an adjustable diameter venturi that is able to handle greater power throughput and yet reduces the likelihood of catastrophic failure during high performance use.
It has been long known that pairing a jet pump with a venturi of certain diameters can affect the pressure of water passing through the pump in relation to the speed in which that water passes through the pump housing, ultimately exiting through a venturi.
The common solution is to match a pump with a venturi to achieve a resulting performance metric. Invariably this requires a compromise between volume of flow, velocity of flow and pressure. It has been difficult, if not impossible to gain performance at both opposing ends of the hydrodynamic performance spectrum.
There have been several attempts to vary the diameter of a jet drive venturi using several theories. Broadly, these attempts can be categorized as bladder style, trap door style or iris style.
The bladder style inflates elastic bladders inside the venturi to affect the net diameter of the output tube. A pump and valve system is provided to inflate and deflate the bladders. The bladders have a tendency to wear out and can be expensive to repair or replace. There are inherent dangers of a high pressure hydraulic system that are also avoided in the present system. There is also a risk of environmental contamination with any hydraulic failure that can occur either inside the hull or outside the hull in the waterways.
The trap door style of adjustment means mechanically articulates a panel that adjustably covers a portion of the exit pathway. These are prone to mechanical breakage due to the brute force required to restrict the ejected water. These systems also have a tendency to redirect the direction of the flow of water exiting the pump which can have a detrimental effect on performance.
The iris style of solution to the adjustable venturi problem utilizes a plurality of overlapping leaves that articulate to form an aperture about an imaginary center. This method is similar to that traditionally used in cameras. It requires many fragile moving parts. Although it appears to be an elegant solution, demanding use in the harsh marine environment with ever increasing horsepower of connected power plants, has proved this design not workable.
Applicant believes what appears to be the closest reference corresponds to U.S. Pat. No. 5,863,229 issued to Matte. However, it differs from the present invention because the present invention evenly compresses about the centerline of thrust. Looking at Matte in FIGS. 10 and 11, at first the means to restrict the diameter of the venturi may appear similar. Matte uses a ring that moves over the venturi and a series of arrows representing flow lines to make it appear as if the diameter is changing between the modes in FIGS. 10 and 11. In fact, these figures do not show any diameter change. The diameter remains fixed at the narrower, inner diameter of the venturi.
Other patents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.